Dust particle injector for hypervelocity accelerators



United States Patent DUST PARTICLE INJECTOR FOR HYPERVELOCITY ACCELERATORS Otto E. Berg, Forest Heights, Md., assignor to the United States of America as represented by the Administrator of the National Aeronautics and Space Administration Filed Aug. 31, 1967, Ser. No. 665,680 Int. Cl. H01j 29/56, 33/02 US. Cl. 315-111 7 Claims ABSTRACT OF THE DISCLOSURE A method and apparatus for use in forming a highly collimated beam of microparticles having a high charge-to-mass ratio and injecting such beam into a electrostatic accelerating tube. The apparatus includes an insulated housing having a particle exit opening; a pair of conically shaped electrodes which are arranged within the housing with their apex portions disposed in a spaced apart facing relationship in alignment with the housing exit opening, the electrode adjacent the housing exit opening having a particle exit passageway extending through the apex portion thereof; and an electrical circuit adapted to control charging of the particles and the application of an electrical field across the electrodes. Particles arranged within the housing are electrostatically charged to distribute the particles adjacent the electrodes, whereafter voltage pulses of appropriate sign are applied to the electrodes to produce a strongly collimated beam of charged particles having a high charge-to-mass ratio; the beam being ejected from the housing through the electrode passageway and housing exit opening, and thereafter injected into an electrostatic accelerating tube.

The invention described herein was made by an employe of the United States Government and may be manufactured and used by or for the Government for governmental purposes without the payment of any royalties thereon or therefor.

The present invention is particularly adapted for use in forming a strongly collimated beam of microparticles having a high charge-to-mass ratio and injecting such beam in an electrostatic accelerating tube which is adapted to accelerate particles within the beam to meteoric velocities. The thus accelerated particles may be employed to simulate micrometeoric impacts to be used, for instance, in sensor calibration and studies of erosion and luminous effects.

Heretofore, it has been well known to accelerate charged particles by an electrical field defined by a pair of spaced electrodes. However, in attempting to employ existing techniques to obtain a beam of charged particles having a charge-to-mass ratio in excess of about conlombs per kilogram, excessive electrode failure is often encountered due to the high potential difference which it is found necessary to apply to the electrodes. Further, by

use of present techniques it is difficult to obtain a strongly collimated beam of such particles.

Accordingly, it is an object of the present invention to provide a method and apparatus for accelerating and focusing mirco-particles having a high charge-to-mass ratio which is not subject to the above mentioned disadvantages.

This and other objects of the present invention will become apparent from the following description taken with the accompanying drawing in which:

FIGURE 1 is a partially sectioned elevational view of the apparatus employed in the practice of the present invention;

FIGURE 2 is a fragmentary view showing a modified electrode design; and

FIGURE 3 is a sectional view illustrating another modified electrode design.

One form of the apparatus employed in the practice of the present invention is generally designated as 1 in FIG- URE 1 and includes an insulated housing 2; first, second, and third electrodes, generally designated as 3, 4, 5 and an electrical control circuit generally designated as 6. As will more fully hereinafter be described, the apparatus is particularly adapted to form and inject a highly collimated beam of particles 7 axially into a hypervelocity acceleration tube 8 of conventional design.

Housing 2 is shown in FIGURE 1 as generally including an upper portion 9, which is provided with a particle exit opening 10 adapted to be disposed in axial alignment with acceleration tube 8; and a tapered lower portion 11, which is adapted to receive a mass of particles 12 which tend to collect under the influence of gravity. Housing lower portion 11 is apertured, as at 13, to receive the third electrode 5, having an enlarged head portion 14 adapted to underlie the collected mass of particles.

For purposes of the present invention, upper housing portion 9 ma be of either circular or rectangular cross section; but lower housing portion 11 is preferably conically shaped to facilitate the collection of particles about the enlarged head portion of the electrode 5. Further, housing 2 is preferably formed of a suitable electrically insulating material, such as Lucite, and grounded in any suitable manner, not shown, to prevent the buildup of undesirable electrical charges thereon, If desired, the entire top of the housing may be removable to permit the admission of particles and to facilitate assembly of the apparatus.

First electrode 3 and second electrode 4, which, as will become clear, function, respectively, as particle attracting and repelling electrodes, are preferably each formed with substantially conically shaped surface portions 15, 1-6, and are arranged within housing 2 with their apex portions 17 and 18, respectively, in facing spaced relationship. Electrode 3 is provided with a particle exit passageway, shown in phantom at 19, which extends through apex portion 17 and is disposed in axial alignment with apex portion 18 of the electrode 4 and housing exit opening 10.

FIGURE 2 illustrates a modification of the design of the second electrode 4', wherein a shallow annular groove 20 is disposed immediately adjacent apex portion 18 to create a small, substantially nipple-shaped tip or head or sphere 21. The discontinuity in electrode surface 16' formed by groove 20 tends to assist in operation of the second electrode in a manner to be fully hereinafter described.

Electrodes 3 and 4 may be supported on opposing side wall portions of housing 2 in any suitable manner, not shown. Further, these electrodes may be formed of any suitable electrode material and be of solid construction, or be hollow, as illustrated in the case of electrode 3 in FIGURE 3. An electrode structure of the type shown in FIGURE 3 results not only in material savings, but facilitates the forming of the particle exit passageway 19'.

Control circuit 6 is shown diagrammatically in FIG- URE l as including a voltage pulser unit 22, which is suitably connected to electrodes 3 and 4, such as by wires 23 and 24, respectively; a battery 25, and a buffer or electrical filter 26, which is arranged between pulser unit 22 and battery 25 and adapted to prevent the appearance of voltage pulses at battery 25 during operation of pulsing unit 22. The elements of control circuit 6 are of conventional design and individually form no part of the present invention.

-In the practice of the preferred form of the present invention, particles collected in mass 12 are positively charged by employing battery 25 to provide a high volt- A ril 28, 1970 0.. E. BERG 3,509,419

DUST PARTICLE INJECTORIFOR HYPERVELOCITY ACCELERATORS Filed Aug. 31, 1967 weer aeum. i 15 'u Lo wvsuroe; orro E. 5526 ray radiation. Furthermore, rather than normally retaining a supply of particles within the housing, particles having a charge thereon may be injected into the housing immediately prior to pulsing the conically shaped electrodes. Also, while the particles have been described as micro particles, such as dust particles, it is anticipated that the present invention is equally suitable for use in forming a highly collimated beam of particles including protons, ions, and electrons. Accordingly, since these and other modifications of the present invention will occur to others skilled in the art in view of the foregoing description, I wish to be limited only by the scope of the appended claims wherein:

What is claimed is:

1. An apparatus for forming a substantially collimated beam of charged particles for injection into an accelerating tube which comprises a housing having a particle exit opening provided in one wall thereof; a first electrode arranged within and insulated from said housing, said first electrode having a particle exit passageway aligned with said exit opening; a second electrode arranged within and insulated from said housing, said second electrode being of a substantially sonically shaped configuration and having the apex portion thereof facing said first electrode in alignment with said passageway and said exit opening; discontinuity means immediately adjacent to said apex portion of said second electrode for segregating particles adjacent said apex portion from those attached elsewhere on the conical surface of said second electrode to increase the degree of beam collimation; and circuit means, said circuit means being adapted to selectively maintain said second electrode at a predetermined potential to permit at lea-st some of said particles, when having a predetermined electrical charge, to be electrostatically attracted to the conical surface of said second electrode, and said circuit means being selectivley adapted to substantially simultaneously apply pulses of voltage of opposite polarity to said electrodes, the polarity of the voltage pulse applied to said second electrode being of like sign to said predetermined charge.

2. The apparatus according to claim 1, wherein said first electrode is of a substantially conically shaped configuration having the apex portion thereof facing said second electrode and said passageway extending through the apex portion thereof.

3. The apparatus according to claim 2, wherein said first electrode is hollow and said passageway is defined by the walls of an aperture passing through said apex portion.

4. The-apparatus according to claim 1, wherein said first and second electrodes are arranged adjacent vertically extending side wall portions of said housing, said housing is provided with a lower portion adapted to receive particles tending to collect in mass under the influence of gravity, a third electrode is arranged within the lower portion of said housing and electrically insulated therefrom, and said circuit means is further adapted to selectivley apply a pulse of electrical potential across said said third electrode and at least one of said first and second electrodes to apply said predetermined charge to and thus effect electrostatic agitation of said particles.

5. The apparatus according to claim 4, wherein said first electrode is of a substantially conically shaped configuration having an apex portion facing said second electrode and said passageway extends through the apex portion thereof.

6. The apparatus according to claim 4, wherein said third electrode is connected to ground and said circuit means is adapted to apply said pulse of electrical potential selectively to said second electrode.

7. The apparatus according to claim '1, wherein said discontinuity means is an annular groove.

References Cited UNITED STATES PATENTS 2,764,707 9/1956 Crawford et a1. 328233 X 3,036,213 5/1962 Dessler et al 328233 X 3,248,586 4/1966 Schlegel 3'l3-2l7 X 3,256,429 6/1966 Perkins et a1. 2504l.9

JAMES W. LAWRENCE, Primary Examiner E. R. LA ROCHE, Assistant Examiner U.S. c1. X.R. 32s 233; 31363, 230; 250-419 

